Servo Transparency is a phenomenon that can be encountered during excessive helicopter maneuvering outside of the flight envelope.[^1] Transparency is affected by airspeed, collective pitch, weight, g-loading, and density altitude[^1] . Single-hydraulic system aircraft are prone to servo transparency at the extremes of the flight envelope.[^2] The maximum servo pressure is limited to prevent overstress of the airframe.[^1] If the aerodynamic load is more than the hydraulic servos can offset, the load forces are transmitted back through the controls to the pilot.[^1] On clockwise-turning rotors the right servo has the highest load when maneuvering as it is on the side of the retreating blade.[^1] Therefore servo transparency results in increasing left-cyclic loads to avoid uncommanded right cyclic motion with down collective movement.[^1] To the pilot, it may feel like the controls are jammed.[^1] This causes a right roll and maybe a pitch up.[^1] To recover, immediately reduce the severity of the maneuver.[^1] The phenomenon itself is self-correcting ,but an abrupt left cyclic movement may occur as the hydraulic power is restored to the servo.[^1]
[[Helicopter Performance]] – at a low power margin, slowing an approach that is too fast may result in servo transparency.
[[Servo Transparency Inducing Situations]]
- LS1648-29-03-REV0-A
- 3287-S-67-Rev-1-EN
Backlinks:
[[Helicopter Control Systems]]